Dual cure epoxy formulations for 3D printing applications

Abstract

The present invention lies in the field of 3D printing methods. In particular, the invention relates to 3D printing methods for the production of a 3D part in a layer-by-layer manner, wherein the printable composition is a pasty epoxy composition comprising at least one epoxy resin, at least one monomer and/or prepolymer that is polymerizable by exposure to radiation and at least one photoinitiator, wherein the pasty epoxy composition has a viscosity factor (1.5/15) of at least 2 at application temperature.

What is claimed: 
     
       1. A method for additive manufacturing a three-dimensional part in a layer-by-layer manner, the method comprising:
 (i) providing a carrier substrate to support the three-dimensional part and a print head connected to a reservoir of a printable composition; 
 (ii) printing the printable composition with the print head in the form of extrudate strands onto the carrier substrate to form a first layer; 
 (iii) printing the printable composition with the print head in the form of extrudate strands onto the first layer to form a second layer; 
 (iv) optionally repeating step (iii) one or more times to form a third layer or the third layer and subsequent layer(s); 
 (v) exposing the formed layers to radiation directly after forming each layer and/or after forming all of the layers; and 
 (vi) curing the formed layers of the printable composition by heating to obtain the three-dimensional part, 
 wherein the printable composition is a pasty epoxy composition comprising:
 at least one epoxy resin; 
 at least one monomer and/or prepolymer that is polymerizable by exposure to radiation; 
 at least one photoinitiator; and 
 at least one adhesion promoter, wherein: 
 
 the pasty epoxy composition has a first viscosity factor (1.5/15) of at least 4 and a second viscosity factor (5/50) at an application temperature, 
 the pasty epoxy composition has a viscosity at a shear rate of 1.5/s of at least 10 Pas, and 
 the first viscosity factor (1.5/15) is greater than the second viscosity factor (5/50). 
 
     
     
       2. The method of  claim 1 , wherein the distance of the print head to the carrier substrate or an already formed layer is equal to or greater than the thickness of the printed extrudate strands. 
     
     
       3. The method of  claim 1 , wherein the second viscosity factor (5/50) at the application temperature is at least 3. 
     
     
       4. The method of  claim 1 , wherein the application temperature is in a range of from 15° C. to 80° C. 
     
     
       5. The method of  claim 1 , wherein the viscosity at the shear rate of 1.5/s is at least 20 Pas. 
     
     
       6. The method of  claim 1 , wherein the at least one epoxy resin comprises an aliphatic epoxy resin. 
     
     
       7. The method of  claim 1 , wherein the at least one monomer and/or prepolymer that is polymerizable by exposure to radiation is selected from the group consisting of di-acrylates, tri-acrylates and mixtures thereof. 
     
     
       8. The method of  claim 1 , wherein the printable composition further comprises an epoxy curing catalyst. 
     
     
       9. The method of  claim 1 , wherein the printable composition further comprises a dual reactive compound. 
     
     
       10. The method of  claim 1 , wherein the printable composition further comprises at least one compound having at least one oxetane group. 
     
     
       11. The method of  claim 1 , wherein the pasty epoxy composition further comprises at least one organic hardener co-polymerizable with the at least one epoxy resin. 
     
     
       12. The method of  claim 1 , wherein the pasty epoxy composition further comprises core-shell particles. 
     
     
       13. The method of  claim 1 , wherein the radiation is ultraviolet (UV) radiation. 
     
     
       14. The method of  claim 5 , wherein the viscosity at the shear rate of 1.5/s is at least 30 Pas. 
     
     
       15. The method of  claim 1 , wherein the at least one epoxy resin is a polyepoxide having an epoxy equivalent of between 110 g/mol and 5000 g/mol. 
     
     
       16. The method of  claim 1 , wherein the at least one epoxy resin is a polyepoxide having an epoxy equivalent of between 130 g/mol and 2000 g/mol. 
     
     
       17. The method of  claim 4 , wherein the application temperature is 25° C. 
     
     
       18. The method of  claim 4 , wherein the application temperature is 55° C.